CN1909536A - Communication method and device for crossing frequency division multiple address-time division multiple address - Google Patents
Communication method and device for crossing frequency division multiple address-time division multiple address Download PDFInfo
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Abstract
The invention relates to a communication method used in OFDMA-TDMA system and a relative device, wherein the system physical frame is formed by two sections of forward sequence and data marks; the first pilot sequence can avoid orthogonal modulation, as the false random sequence emitted directly, to fix the start time of DFT calculation; the second pilot sequence is orthogonally modulated with the data mark to form OFDM mark to be emitted. Compared with traditional method, the invention can avoid demodulating pilot mark at the start of DFT calculation, to effectively time the mark and improve the accuracy of evaluated valve of signal channel.
Description
Technical field
The present invention relates to wireless communications method and device, particularly adopt the information transmission system of the WLAN (wireless local area network), fixed wireless access, mobile communication, ground digital television broadcast etc. of OFDM technology, more particularly, the present invention relates to a kind of crossing frequency division multiple address-time division multiple address communication means and device that can carry out the symbol timing and improve the channel guess value accuracy.
Background technology
Along with the fusion gradually of wireless network, multimedia technology and internet, people are more and more higher to the requirement of the type of radio communication service and quality.For satisfying the requirement of radio multimedium and high speed data transfers, need the Development of New Generation wireless communication system.In the new generation of wireless system, to network layer, will extensively adopt some new technologies, as OFDM (OFDM) etc. from physical layer, media access control layer.
OFDM is divided into many orthogonal sub-channels to channel at frequency domain; whole wideband frequency selective channel is divided into the subchannel of relatively flat; simultaneously, insert Cyclic Prefix (CP) as protection interval (GI), reduced intersymbol interference (ISI) greatly at each OFDM intersymbol.Because OFDM has advantages such as ability of anti-multipath is strong, the application that it has been succeeded in systems such as xDSL, DVB, DAB and WLAN, IEEE 802.16.At present, in the Long Term Evolution plan (LTE) of 3G (Third Generation) Moblie standardization body (3GPP), also it as improve down (on) key technology of row channel transmission rate and capacity.
The ofdm system that has proposed supports that all the multi-user inserts.In the multi-user OFDM system, the selection of multi-access mode is a major issue.Existing multi-access mode all can be used for ofdm system as time division multiple access (TDMA), frequency division multiple access (FDMA), code division multiple access (CDMA).In the OFDM tdma system, each user occupies different time-gap, and in each time slot, all subcarriers are all distributed to same user, shown in Fig. 1 (a).The advantage of TDMA is can be according to different data transfer rate dynamic assignment time slots, and receiver receives the base station and sends to its information in assigned timeslot, reduced the receiver power consumption.Medium access control (MAC) agreement of European Wireless local area network standard HiperLAN/2 has adopted TDMA.In OFDM FDMA, in each OFDM symbol,, be also referred to as OFDM (OFDMA), shown in Fig. 1 (b) for each user distributes a part of subcarrier in all carrier waves.Its advantage is when transmitting terminal known channel state information (CSI), can be each user's dynamic assignment subcarrier, and it has been used for cable TV CATV transmission system.
The mixing multiple access technology OFDMA-TDMA that adopts OFDMA to combine with TDMA has the advantage of the two, and it can be the different user distributing carrier wave in each time slot, and meticulousr time-frequency resource allocating is provided, and flexibility is stronger.This technology has been applied to the novel wireless communication system based on OFDM, in broadband wireless access IEEE 802.16 standards and IEEE 802.20 standards based on Flash-OFDM, all adopts OFDMA-TDMA as access mode.Recently, in 3GPP LTE motion, some companies advise that also an OFDMA-TDMA is as downlink transmission mode.OFDMA-TDMA has two kinds of different implementation methods, and a class is the OFDMA-TDMA of frequency diversity, is characterized in distributing subcarrier in frequency domain to the user randomly at each time slot, shown in Fig. 2 (a); Another kind of is the OFDMA-TDMA of frequency domain dispatching, and its characteristics adopt dispatching algorithm to give user's distributing carrier wave, shown in Fig. 2 (b) at each time slot.First kind OFDMA-TDMA has been applied in IEEE 802.16 standards, and the second class OFDMA-TDMA system has the high advantage of spectrum efficiency, but also less to its research at present.The technical foundation of two class OFDMA-TDMA remains OFDM, and following business is to transmit Packet Service mostly, because Packet Service has the burst feature, so a key technology of ofdm system is to need accurately to realize that symbol regularly.
In traditional ofdm system, as IEEE 802.11a standard, its frame format as shown in Figure 3.Its leading pilot signal of forming by two OFDM symbols that comprises, wherein first pilot signal is that pseudorandom (PN) sequence is carried out the symbol that QPSK modulation obtains, it as regularly, thick synchronous etc.Second pilot signal carried out the symbol that the BPSK modulation obtains to pseudorandom (PN) sequence, and it is as channel estimating and smart Frequency Synchronization etc.It after leading data symbol after the modulation.
During emission, flow through coding, modulation back of input information bits forms data symbol, inserts frequency pilot sign before data symbol.Then, these symbols are carried out sewing (CP) against discrete fourier transform (IDFT), adding circulation embedding.At last, after carrier modulation, be transmitted into channel, as shown in Figure 4.Existing ofdm communication system as IEEE 802.16 etc., has all adopted this communication mode of launching behind the frequency domain that frequency pilot sign is transformed to.During reception, need with its discrete fourier transform (DFT) to the laggard row of time domain regularly, processing such as synchronous.Such operation can make frequency pilot sign obtain ability of anti-multipath through multi-carrier modulation.But also there are some shortcomings in this mode, because carrying out DFT and separate timing receiving pilot tone and data, the initial computing that needs earlier to determine the DFT window according to pilot signal constantly.But determine that the DFT computing needs again earlier frequency pilot sign to be carried out the DFT demodulation constantly, so there are the relation of interdependence, influence between the two in symbol timing and DFT demodulation.If DFT calculates constantly the not zero hour of corresponding frame, promptly there is deviation, then can have influence on the precision of operations such as subsequently timing, Frequency Synchronization, and then reduce the overall performance of system.
The list of references tabulation:
[1]3GPP?R1-050251，Nokia，Uplink?Considerations?for?UTRANLTE，RAN1?40bis；
[2]3GPP?R1-050245，Motorola，Uplink?Multiple?Access?forEUTRA，RAN1?40bis；
[3]3GPP?R1-050248，NTT?DoCoMo，Uplink?Multiple?AccessScheme?for?Evolved?UTRA，RAN1?40bis；
[4]3GPP?R1-050254，Ericsson，Evolved?UTRA，Uplinktransmission?scheme，RAN1?40bis；
[5]3GPP?R1-050260，Siemens?AG，Multiple?Access?SchemeEvaluation?for?the?SI’Evolved?UTRA?and?UTRAN’Uplink，RAN140bis；
[6]3GPP?R1-050269，Samsung，Uplink?Multiple?Access?forEvolved?UTRA?Radio?Interface，RAN1?40bis；
[7]3GPP?R1-050390，ZTE，EUTRA?Uplink?Multiple?Access?forDownlink?and?Uplink，RAN1?41bis。
Summary of the invention
The object of the present invention is to provide the communication means and the device of a kind of OFDMA-TDMA of being used for system, can eliminate symbol regularly and DFT demodulation interactional problem between the two, and improve the accuracy of channel guess value.
According to a first aspect of the invention, proposed a kind of crossing frequency division multiple address-time division multiple address communication means, may further comprise the steps: message bit stream is encoded and modulated to form data symbol; Select the time domain autocorrelation good and the low pseudo random sequence of cross correlation is formed for symbol first pilot frequency sequence regularly; Select the frequency domain autocorrelation good and the low symbol of cross correlation forms second pilot signal; Before second frequency pilot sign is attached to data symbol, form packet to be modulated; First pilot frequency sequence is carried out carrier modulation, and modulated first pilot frequency sequence is transmitted into channel; And packet IDFT that will be to be modulated is modulated to the OFDM symbol, and is transmitted into channel.
Preferably, the good and low pseudo random sequence of cross correlation of described time domain autocorrelation is from M sequence, Gold sequence, Hadamard sequence, has the LAS sign indicating number of zero their cross correlation and select.
According to a second aspect of the invention, proposed a kind of crossing frequency division multiple address-time division multiple address communicator, it is characterized in that comprising: data symbol forms device, is used for the message bit stream of input is just encoded and modulated to form data symbol; First pilot frequency sequence forms device, is used to select the time domain autocorrelation good and the low pseudo random sequence of cross correlation is formed for symbol first pilot frequency sequence regularly; Second pilot frequency sequence forms device, is used to select the frequency domain autocorrelation good and the low symbol of cross correlation forms second pilot signal, and before second frequency pilot sign is attached to data symbol, forms packet to be modulated; The inverse discrete Fourier transform device is used for the packet of modulation is carried out inverse discrete Fourier transform, so that be modulated to OFDM symbol.
Description of drawings
Below with reference to accompanying drawings, the preferred embodiments of the present invention are described in detail, wherein:
Fig. 1 (a) and 1 (b) show the schematic diagram of OFDM TDMA/FDMA example;
Fig. 2 shows the schematic diagram of OFDMA-TDMA example;
Fig. 3 shows the schematic diagram of IEEE 802.11a frame format;
Fig. 4 shows the block diagram of traditional OFDM emitter;
Fig. 5 shows the schematic diagram of physical frame used in this invention;
Fig. 6 shows the block diagram according to the OFDM emitter of the embodiment of the invention; And
Fig. 7 shows the pilot tone according to the embodiment of the invention, the flow chart of data emitting method.
Embodiment
Below in conjunction with accompanying drawing the present invention is specified.Be noted that described embodiment only is for illustrative purposes, rather than limitation of the scope of the invention.Described various numerical value is not to be used to limit the present invention, and these numerical value can carry out any suitable modification according to those of ordinary skills' needs.
Fig. 5 shows physical frame used in this invention.The physical frame of OFDM emission is by forming leading (comprising frequency pilot sign Pilot1 and Pilot2) and data symbol.Wherein Pilot1 is mainly used in the frame detection, i.e. symbol timing, and it is the pseudorandom PN sequence of a non-modulated.This PN sequence can adopt the pseudo random sequence that has good autocorrelation in time domain, as M sequence, Gold sequence, Hadamard sequence, and the LAS sign indicating number with zero their cross correlation that proposes recently etc.Pilot2 is as channel estimating, frequency offset estimating etc., and it can adopt defined symbol in the standards such as IEEE802.11a, HiperLAN/2, or employing has good autocorrelation and the low sequence of cross correlation at frequency domain.
Fig. 6 shows the block diagram according to OFDM emitter of the present invention.Form in the unit 601 encoded the and modulation back formation data symbol of the message bit stream of input at data symbol.In pilot plug-in unit 602, before data symbol, insert frequency pilot sign and form armed packet.
Then; frequency pilot sign is divided into two branch road emissions; wherein be used for symbol pilot frequency sequence Pilot1 regularly to what timing pilot tone generation unit 607 produced directly by being transmitted into channel after the carrier modulation; the frequency pilot sign Pilot2 that is used for channel, frequency offset estimating and data are input to IDFT unit 603 carry out quadrature modulation; insert protection at interval before inserting the symbol of cyclic prefix CP unit 604 after modulation; be CP; form the OFDM symbol, after RF unit 605 carries out carrier modulation, be transmitted into channel again by antenna 606.
Fig. 7 shows the flow chart according to crossing frequency division multiple address-time division multiple address communication means of the present invention.
At step S701, message bit stream is encoded and modulated to form data symbol; In step 702, select good and the pseudo random sequence that cross correlation is low of time domain autocorrelation and the frequency domain autocorrelation is good and symbol that cross correlation is low is formed pilot signal; In step 703, select the frequency domain autocorrelation good and the low symbol of cross correlation forms second pilot signal; In step 704, frequency pilot sign is attached to data symbol before to form armed packet; In step 705, extraction is used for the pilot frequency sequence of symbol timing and it is carried out carrier modulation from packet, is transmitted into channel then; In step 706, the frequency pilot sign and the data symbol that are used for channel, frequency offset estimating etc. after being modulated to the OFDM symbol, IDFT are transmitted into channel again.
In traditional ofdm system, all frequency pilot signs and data are all carried out launching after the IDFT modulation again.Different therewith, in communication means of the present invention, directly emission is without the part frequency pilot sign of IDFT modulation earlier, and receiving terminal utilizes this symbol to carry out symbol regularly, the initial position when determining to carry out the IDFT computing, and write down this moment.Then, from this constantly,, comprise the pilot tone and the data that are used for channel estimating etc., carry out the DFT demodulation the OFDM symbol that receives.By this launching technique, overcome in the conventional method, determine that the DFT computing needs the demodulation pilot frequency symbol constantly, and the demodulation pilot frequency symbol needs the ambiguousness in the known initial moment of DFT computing, can carry out symbol effectively regularly, and improve the precision of subsequent communication channel, frequency offset estimating, and be of value to the raising systematic function.
For regularly influencing each other with the IDFT computing, the solution symbol brings the problem of error, the present invention designs a kind of frame structure, it leading by having good pseudo random sequence and good oneself (mutually) correlation of frequency domain and the low sequence of cross correlation is formed from (mutually) correlation of time domain.The good correlation here mainly refers to the autocorrelation value height and cross correlation is low.When adopting the M sequence, with initial condition 001 and proper polynomial f (z as first section sequence
-1)=z
3+ z+1, f (z
-1)=z
3+ z
2+ 1 cycle that produces was that 7 sequence is: 0,010 1,110 0,101 1,100 10111.Be compatible as far as possible existing standard, the second section sequence that is used for channel estimating adopts the sequence of existing standard, as
Adopt sequence { 0000001 1-1-1 1 1-1 1-11 1111 1-1-1 1 1-1 1-1 11110 1-1-1 1 1-1 1-1 1-1-1-1-1-1 1 1-1-1 1-1 1-1 11110000 0} of IEEE 802.11a.Like this, whole frame format is:
(0,010 1,110 0,101 1,100 10111) (0 000001 1-1-1 1 1-11-1 11111 1-1-1 1 1-1 1-1 11110 1-1-1 1 1-1 1-1 1-1-1-1-1-1 1 1-1-1 1-1 1-1 11110000 0) (... data ...).
In order to compare, provide the previous video frames form of general IEEE 802.11a below:
; (0 0000000 1+j, 00 0-1-j, 000 1+j, 00 0-1-j, 0 00-1-j, 000 1+j, 000000 0-1-j, 00 0-1-j, 000 1+j, 00 01+j, 000 1+j, 000 1+j 000000 0); (0 000001 1-1-11 1-1 1-1 11111 1-1-1 1 1-1 1-1 11110 1-1-1 11-1 1-1 1-1-1-1-1-1 1 1-1-1 1-1 1-1 1111000 00); (... data ...).
Can find that the frame structure that the present invention proposes is shorter, like this, the hardware resource that takies still less.And utilize it at first to carry out frame and detect, find the original position of IDFT computing earlier; Then, demodulating ofdm symbol exactly.When launching each packet, at first after carrier modulation, be transmitted into channel being used for symbol pilot frequency sequence (0,010 1,110 0,101 1,100 10111) regularly; Then, the frequency pilot sign (0 000001 1-1-1 1 1-11-1 11111 1-1-1 1 1-1 1-1 11110 1-1-1 1 1-1 1-1 1-1-1-1-1-1 1 1-1-1 1-1 1-1 11110000 0) and the data symbol that are used for channel, frequency offset estimating etc. after being modulated to the OFDM symbol, IDFT are transmitted into channel again after carrier modulation.
Although illustrated and described the present invention at exemplary embodiments, will be understood by those skilled in the art that, under the situation that does not break away from the spirit and scope of the present invention, can carry out various other change, replacement and interpolations.Therefore, the present invention should not be understood that to be limited to above-mentioned particular instance, and should be limited by claims.
Claims (5)
1, a kind of crossing frequency division multiple address-time division multiple address communication means may further comprise the steps:
Message bit stream is encoded and modulated to form data symbol;
Select the time domain autocorrelation good and the low pseudo random sequence of cross correlation is formed for symbol first pilot frequency sequence regularly;
Select the frequency domain autocorrelation good and the low symbol of cross correlation forms second pilot signal;
Before second frequency pilot sign is attached to data symbol, form packet to be modulated;
First pilot frequency sequence is carried out carrier modulation, and will be transmitted into channel through first pilot frequency sequence of carrier modulation so that the packet of being launched is carried out symbol regularly; And
Packet inverse discrete Fourier transform to be modulated is modulated to OFDM symbol, and is transmitted into channel.
2, crossing frequency division multiple address-time division multiple address communication means according to claim 1 is characterized in that the good and low pseudo random sequence of cross correlation of described time domain autocorrelation is from M sequence, Gold sequence, Hadamard sequence, has the LAS sign indicating number of zero their cross correlation and select.
3, a kind of crossing frequency division multiple address-time division multiple address communicator is characterized in that comprising:
Data symbol forms device, is used for the message bit stream of input is just encoded and modulated to form data symbol;
First pilot frequency sequence forms device, is used to select the time domain autocorrelation good and the low pseudo random sequence of cross correlation is formed for symbol first pilot frequency sequence regularly;
Second pilot frequency sequence forms device, is used to select the frequency domain autocorrelation good and the low symbol of cross correlation forms second pilot signal, and before second frequency pilot sign is attached to data symbol, forms packet to be modulated;
The inverse discrete Fourier transform device is used for the packet of modulation is carried out inverse discrete Fourier transform, so that be modulated to OFDM symbol.
4. communicator according to claim 3 wherein also comprises:
Insert the Cyclic Prefix device, be used for forming OFDM symbol through inserting protection before the symbol of inverse discrete Fourier transform at interval.
5. first pilot frequency sequence that communicator according to claim 3, wherein said first pilot frequency sequence form device formation is transmitted into channel through after the carrier modulation, so that the packet of being launched is carried out symbol regularly.
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| CN101286753B (en) * | 2007-04-11 | 2012-11-14 | 中兴通讯股份有限公司 | Lead code sending and receiving method for wideband wireless communication system |
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| WO2009043310A1 (en) * | 2007-09-27 | 2009-04-09 | Beijing Xinwei Telecom Technology Inc. | Method, device and system for sending and receiving user signals in an ofdma system |
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| CN107409328B (en) * | 2015-03-11 | 2020-11-03 | 华为技术有限公司 | OFDMA transmission method, Access Point (AP) and site |
| CN107409328A (en) * | 2015-03-11 | 2017-11-28 | 华为技术有限公司 | OFDMA transmission methods, access point AP and website |
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| CN107276627A (en) * | 2016-04-08 | 2017-10-20 | 深圳超级数据链技术有限公司 | Signal processing method and system |
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